Microhybrid electric vehicles incorporate start stop systems, which automatically shut down the engine of the vehicle to minimize engine idling conditions when the vehicle is stationary, and restart the engine when the vehicle starts moving again. This substantially reduces the vehicle's fuel consumption, and emissions from the vehicle. Specifically, the start-stop technology is extremely advantageous when a vehicle is running under traffic jams conditions, or it frequently stops and spends significant time at the traffic signals. In most of the microhybrid electric vehicles, the start-stop technology shuts down the engine when the driver presses the brake pedal or the clutch to stop the car. The engine is restarted when the brake pedal is released (in case of automatic transmissions) and/or the clutch is depressed again (in case of vehicles incorporating manual transmission) prior to selecting the gear for moving the car. In certain cases, the vehicle's engine may also restart if the electrical power demanded by one or more vehicle's subsystems, such as, the air conditioning system, is relatively higher.
Alternators are used in microhybrid vehicles to charge the battery, and to power the electrical systems of the vehicle when the engine is running. When the start-stop system of a vehicle turns the engine off, the vehicle's alternator is also switched off, and the major sub-systems of the vehicle, including the infotainment system, the climate control system, etc., draw power from the battery of the vehicle for operation. Since the alternator shuts down in response to the shutting down of the vehicle's engine, the battery cannot be charged, and it starts draining, as the electrical subsystems draw power from the battery of the vehicle. Therefore, the engine may need to be restarted after a specific time, to avoid a condition where the operation of the electrical subsystems of the vehicle may be effected due to battery drainage and corresponding low electrical system voltage. This may occur in a situation where the vehicle's engine has been shut down by the auto start-stop system of the vehicle, for a relatively long time. Further, in a case where the battery of a vehicle drains to a certain minimum level, subsequent low electrical system voltage may cause undesired performance of the electrically driven subsystems.
To overcome the above problem, many microhybrid vehicles monitor various parameters within the vehicle, to minimize obstructions to proper operating conditions of the electrical components and subsystems of the vehicle during engine stop conditions. In some conventional attempts, a battery management module of the vehicle uses a fixed value of the inrush current the starter motor of the vehicle will draw, to determine availability of the engine start-stop feature. The inrush current value at the starter motor of the vehicle' engine directly affects the electrical systems' voltage. However, if the battery management module uses a fixed programmed value for the starter motor inrush current, there may be certain neglected/unidentified cases where the battery of the vehicle may still have enough power, and the stop-start operation may be left unutilized or underutilized. Other attempts to maximize the start-stop operation in a vehicle have also not been substantially successful so far.
Considering the problems mentioned above, and other shortcomings in the art, there exists a need for a method to maximize the availability of start-stop operation in a microhybrid electric vehicle.